菟丝子提取物在PC12细胞株中的神经营养因子样活性

以常用的PC12细胞株为实验模型,考察了菟丝子提取物诱导PC12细胞分化及对相关激酶活性的影响.发现该提取物在诱导PC12细胞分化的同时,可明显提高有丝分裂原激活的蛋白激酶(MAPK)磷酸化.MAPK激酶的特异抑制剂PD98059,能够有效地抑制菟丝子提取物诱导PC12细胞中MAPK的磷酸化和突起的延伸,表明该提取物诱导PC12细胞分化可能与MAPK途径有关.同时还发现,该提取物能一定程度地抑制去血清引起的细胞凋亡,表明它具有一定的神经营养因子样作用.     

丝裂原活化蛋白激酶激活蛋白激酶(MK)研究进展

丝裂原活化蛋白激酶(MAPK)信号通路介导多种重要的细胞生理反应.对下游蛋白激酶的磷酸化是MAPK家族成员发挥生理作用的重要方式.在MAPK的下游存在3个结构上相关的MAPK激活蛋白激酶(MAPKAPKorMK),即MK2,MK3和MK5.在被MAPK激活后,MK可将信号传递至细胞内不同靶标,从而在转录和翻译水平调节基因表达,调控细胞骨架和细胞周期,介导细胞迁移和胚胎发育.最近,在基因敲除研究的基础上,不同MK亚族成员之间的功能区分已经逐渐明晰,使我们对于MK的认识有了长足的进步.     

巨噬细胞免疫调变信号:Raf-1,MAPK p44,MAPK p42和p38 MAPK的研究

为了了解巨噬细胞免疫调变机理,我们应用LPS和PMA处理小鼠抑制性巨噬细胞,观察到Ras下游信号分子Raf-1,分裂原激活蛋白激酶MAPK p44,MAPK p42和p38 MAPK均被活化,发现forskolin能增强p38 MAPK的活性,进一步提示PKC和PKA途径增强了p38 MAPK的磷酸化效应,为我们了解LPS如何激活p38 MAPK信号通路提供了一个新的机会。     

谷胱甘肽S-转移酶Pi在MAPK途径中的调节作用

谷胱甘肽S-转移酶(glutathione S-transferases,GSTs)是细胞内降解生物异源物质(xenbiotics)的一类酶,GSTπ／GSTpi／GSTp是人体内的一种重要活性亚型;有丝分裂原激活的蛋白激酶(mitogen—activated protein kinase,MAPK)途径能够调节真核细胞凋亡、增殖、分化和应激。1999年国际上首次报道GSTpi能够在MAPK信号途径中起调节作用,其作用机制如下：在正常生长条件下,GSTpi以单体形式与JNK(c—Jun N—terminal kinase)形成复合物,抑制JNK活性;UV照射或H2O2处理细胞后,GSTpi自身形成二聚体／多聚体,导致GSTpi—JNK复合物解离,JNK的抑制被解除,JNK被磷酸化激活后激活转录因子c—Jun,c—Jun的激活能进一步促进GSTpi基因的转录,进而合成新的GSTpi蛋白单体,该单体又能反馈抑制JNK。后续研究发现GSTpi也能够抑制JNK激酶的上游激酶ASK1的活性。上述研究揭示GSTpi酶在细胞内除能通过降低异源物质而改变细胞的ROS平衡外,其蛋白本身还具有特异性地抑制MAPK信号转导途径中JNK激酶和JNK上游激酶的新功能。     

MKP-1在结核分枝杆菌感染中的作用和研究进展

有丝分裂原激活的蛋白激酶(Mitogen-Activated Protein Kinase,MAPK)信号通路是细胞感知外源性刺激并作出有效免疫应答的最重要的细胞内信号通路之一。近年来的研究表明:MAPK的表达异常与结核病的发生、发展密切相关。MAPK磷酸酶(MAPK phosphatases,MKPs)是一类在细胞内水解MAPKs家族的磷酸酶,通过负向调控MAPKs的活性,从而在调节细胞的应激、分化、增殖、凋亡等过程中发挥重要的作用,其中MKP-1是MKPs家族中被报道最多的成员,具有最强的去磷酸化能力。本文综述了MKP-1在结核分枝杆菌感染中的作用和研究进展。     

MAPK信号通路在辐射应答中的作用

丝裂原活化蛋白激酶（MAPK）超家族是介导细胞反应的重要信号系统,主要由MAPK、MAPK激酶（MAPKK）、MAPKK激酶（MAPKKK）等3类保守的蛋白激酶组成,通过级联反应不断磷酸化下游靶蛋白而参与细胞的增殖、分化、衰老、凋亡。辐射损伤使细胞膜受体和其他感应分子激活细胞内的MAPK信号通路,产生一系列应答反应。简要介绍MAPK家族中各条通路在辐射应答中的作用。     

凋亡信号调节激酶1信号通路在肾脏疾病中的作用

凋亡信号调节激酶1(apoptosis signal-regulating kinase 1, ASK1)是丝裂原激活蛋白激酶激酶激酶(mitogen-activated proteinkinase kinases kinase, MAP3K)的家族成员之一,可以响应氧化应激、内质网(endoplasmic reticulum, ER)应激等多种应激刺激,从而激活下游丝裂原激活蛋白激酶(mitogen-activated protein kinase, MAPK)中的c-Jun N末端激酶(c-Jun N-terminal kinase, JNK)和p38丝裂原激活蛋白激酶(p38 mitogen-activated protein kinase, p38 MAPK)信号通路,调节细胞凋亡、炎症和纤维化,介导急性肾损伤(acute kidney injury, AKI)、糖尿病肾病(diabetic kidney disease, DKD)、心肾综合征(cardiorenal syndrome, CRS)等多种肾脏疾病的进展。本文讨论了ASK1主要的激活和失活机制及其在多种肾脏疾病进展...     

MAPK和p90rsk在大鼠卵泡发育中的表达与活性

利用免疫组织化学方法研究丝裂原激活蛋白激酶(mitogen-activated protein kinases, MAPK)及其底物之一p90rsk在大鼠卵泡发育过程中的表达与活性.结果表明,非活性形式的MAPK存在于大鼠各生长期卵泡的卵母细胞和颗粒细胞中,但磷酸化活性形式的MAPK只存在于部分具有分裂增殖活性的颗粒细胞中.MAPK的作用底物p90rsk只在各期卵泡的卵母细胞中表达,在颗粒细胞中无着色,说明MAPK信号级联在卵母细胞和颗粒细胞中具有不同的作用方式.另外,胎鼠卵巢的免疫组化染色结果显示,MAPK在卵原细胞增殖过程中具有活性,表明MAPK信号级联在这一过程中起作用.     

Smad4分子在ERK/MAPK信号转导通路中的作用

为了探讨在人永生化支气管上皮细胞BEP2D细胞中,Smad4分子对 ERK/MAPK通路的作用,我们用RNA干扰的方法分别设计了两对Smad4 siRNA,并使BEP2D细胞中Smad4靶向沉默,用Western印迹分析了细胞内ERK激酶和MEK激酶磷酸化水平的变化.结果发现,当Smad4表达沉默后,ERK激酶磷酸化水平未变,MEK激酶磷酸化水平有所降低;再加TGF-β1诱导后ERK激酶和MEK激酶磷酸化水平均显著降低至基础水平以下.结果表明在BEP2D细胞中,Smad4的缺失抑制TGF-β1对ERK/MAPK通路的活化,故提出TGF β活化ERK/MAPK通路需要Smad4存在的假设.     

转化生长因子β激活性激酶在胶质细胞信号转导中的作用机制

丝裂原激活蛋白激酶（MAPK）和 NFκB介导了炎症细胞转录活性的信号转导过程.转化生长因子β激活性激酶（TGFβ-activated kinase 1,TAK1）是这些转导通路的上游激酶.通过在胶质细胞株中瞬时转染TAK1和它的结合蛋白因子（TAK1-binding protein1 TAB1）基因,或与iNOS(可诱导型氧化氮合酶基因)启动子报告基因（iNOS-Luc）质粒共转染,探讨中枢两类胶质细胞在炎症反应过程中TAK1诱导iNOS 和细胞因子表达的作用机制.结果显示,TAK1明显激活iNOS 和细胞因子（TNFα、IL-1、IL-6）的表达活性. 而且当使用它的下游激酶p38 MAPK、JNK和NFκB的抑制剂（SB203580、SP620125和CAPE）后,这些表达活性明显被抑制.用IκBα的磷酸化突变体质粒(IκBαM)共转染胶质细胞株,能完全抑制iNOS的表达活性.研究结果提示：在胶质细胞内的p38 MAPK、JNK和NFκB信号介导的iNOS和细胞因子的转录表达过程中,TAK1起着非常重要的调节作用.     

Protein kinase C-mediated tyrosine phosphorylation of paxillin and focal adhesion kinase requires cytoskeletal integrity and is uncoupled to mitogen-activated protein kinase activation in human hepatoma cells

Treatment of cultured human hepatoma HepG2 cells with the protein kinase C (PKC) activator, 12-O-tetradecanoylphorbol-13-acetate (TPA), results in an increase in tyrosine phosphorylation of several proteins, including the focal adhesion kinase (FAK) and paxillin using anti-phosphotyrosine Western blotting and immunoprecipitation. However, when cells are in suspension or in the presence of cytochalasin D which disrupts the intracellular network of actin microfilaments, TPA loses its ability to stimulate tyrosine phosphorylation of FAK and paxillin but it still activates mitogen-activated protein kinase (MAPK) and induces PKC translocation from cytosol to the membrane in HepG2 cells. On the other hand, PD98059, a specific inhibitor of mitogen-activated protein kinase kinase, blocks TPA-induced MAPK activation but has no effect on TPA-induced tyrosine phosphorylation. Our findings suggest that TPA-induced tyrosine phosphorylation of FAK and paxillin in human hepatoma cells is PKC dependent and requires the integrity of the cell cytoskeleton but is uncoupled to the signal transduction pathway of PKC leading to the translocation of PKC and MAPK activation.     

蓖麻毒素诱导肝癌细胞生成一氧化氮合酶——免疫组织化学研究

应用免疫组织化学方法观察不同浓度蓖麻毒素作用于肝癌细胞不同时间后,对iNOS的诱导作用。结果显示,未受蓖麻毒素作用的肝癌细胞胞浆iNOS呈阴性反应;当受到蓖麻毒素诱导后,才能在胞浆内合成,不同浓度的蓖麻毒素对肝癌细胞诱导iNOS的产生没有明显差别,而蓖麻毒素诱导iNOS的表达有明显的时间依赖性,2h没有表达,4h才出现,随着时间的延长,到8h时仍然有明显的表达,由于iNOS的合成涉及基因转录,蛋白质合成等过程,故需诱导数小时后显示酶活性,但一经诱导生成,酶活性持续时间长,蓖麻毒素诱导iNOS的产生在抗癌应用中具有重要的价值。     

Interaction of the Hepatitis B Spliced Protein with Cathepsin B Promotes Hepatoma Cell Migration and Invasion

Hepatitis B spliced protein (HBSP) is involved in the pathogenicity and/or persistence of hepatitis B virus (HBV). Chronic HBV infection is one of the most important risk factors for the development of hepatocellular carcinoma (HCC). However, whether or not HBSP contributes to the progression of HBV-associated HCC remains unknown. This study reports that overexpression of HBSP in human hepatoma cells increased cell invasion and motility. Conversely, small interfering RNA (siRNA)-mediated knockdown of HBSP expression inhibited migration and invasion. By glutathione S-transferase (GST) pulldown, coimmunoprecipitation, and a mammalian two-hybrid assay, HBSP was found to directly interact with cathepsin B (CTSB). Similar to HBSP knockdown, knocking down CTSB also reduced cell migration and invasion. Furthermore, the HBSP-overexpressing hepatoma cells were shown to have increased expression and activity of matrix metalloproteinase-9 (MMP-9) and urokinase-type plasminogen activator (uPA), and overexpression of HBSP significantly enhanced tumor-induced vascularization of endothelial cells. In contrast, knockdown of either HBSP or CTSB by siRNA resulted in inhibition of the two proteolytic enzymes and of the in vitro angiogenesis. Expression of HBSP in the hepatoma cells appeared to activate the mitogen-activated protein kinase (MAPK) and Akt signaling pathway, as evidenced by increases in phosphorylation of p38, Jun N-terminal protein kinase (JNK), extracellular signal-regulated kinase (ERK), and Akt. Taken together, these findings imply that interaction of HBSP with CTSB may promote hepatoma cell motility and invasion and highlight new molecular mechanisms for HBSP-induced HCC progression that involve the secretion and activation of proteolytic enzymes, increased tumor-induced angiogenesis, and activation of the MAPK/Akt signaling, thereby leading to the aggressiveness of hepatoma cells.     

Anti-proliferative and pro-apoptotic effect of carvacrol on human hepatocellular carcinoma cell line HepG-2

Carvacrol is one of the members of monoterpene phenol and is present in the volatile oils of Thymus vulgaris, Carum copticum, origanum and oregano. It is a safe food additive commonly used in our daily life, and few studies have indicated that carvacrol has anti-hepatocarcinogenic activities. The rationale of the study was to examine whether carvacrol affects apoptosis of human hepatoma HepG2 cells. In this study, we showed that carvacrol inhibited HepG2 cell growth by inducing apoptosis as evidenced by Hoechst 33258 stain and Flow cytometric (FCM) analysis. Incubation of HepG2 cells with carvacrol for 24 h induced apoptosis by the activation of caspase-3, cleavage of PARP and decreased Bcl-2 gene expression. These results demonstrated that a significant fraction of carvacrol treated cells died by an apoptotic pathway in HepG2 cells. Moreover, carvacrol selectively altered the phosphorylation state of members of the MAPK superfamily, decreasing phosphorylation of ERK1/2 significantly in a dose-dependent manner, and activated phosphorylation of p38 but not affecting JNK MAPK phosphorylation. These results suggest that carvacrol may induce apoptosis by direct activation of the mitochondrial pathway, and the mitogen-activated protein kinase pathway may play an important role in the antitumor effect of carvacrol. These results have identified, for the first time, the biological activity of carvacrol in HepG2 cells and should lead to further development of carvacrol for liver disease therapy.     

Interferon alpha and ribavirin collaboratively regulate p38 mitogen-activated protein kinase signaling in hepatoma cells

Signaling events triggered by interferon alpha (IFN-α) and ribavirin are involved in anti-hepatitis C virus (HCV) action. The p38 mitogen-activated protein kinase (MAPK) pathway plays an important role in HCV pathogenesis. Effects of IFN-α and ribavirin on p38 MAPK signaling were investigated in human hepatoma cells. Type I IFN receptor 2 (IFNAR2) mediated IFN-α-induced p38 MAPK phosphorylation. Also, p38 MAPK phosphorylation was enhanced by ribavirin. Treatment for 48 h with a combination of IFN-α and ribavirin increased p38 MAPK phosphorylation, whereas the treatment for 72 h reduced p38 MAPK phosphorylation. Cell culture-derived HCV (HCVcc) infection dramatically increased p38 MAPK phosphorylation and such phosphorylation was inhibited by IFN-α or ribavirin. Moreover, siRNA-mediated knockdown of p38 MAPK resulted in enhancement of ribavirin-dependent HCV RNA replication. These results suggest that regulation of p38 MAPK signaling by IFN-α and ribavirin might contribute to anti-HCV action.     

Oleoylethanolamide,a natural ligand for PPAR-alpha,inhibits insulin receptor signalling in HTC rat hepatoma cells

Oleoylethanolamide (OEA) is a lipid mediator belonging to the fatty acid ethanolamides family. It is produced by intestine and adipose tissue. It inhibits food intake and body weight gain, and has hypolipemiant action in vivo, as well as a lipolytic effect in vitro. OEA is a PPAR-alpha agonist, and recently it has been found that OEA is an endogenous ligand of an orphan receptor. Previously, we have shown that OEA inhibits insulin-stimulated glucose uptake in isolated adipocytes, and produces glucose intolerance in rats. In the present work, we have studied another insulin target cell, the hepatocyte using a rat hepatoma cell line (HTC), and we have studied the cross-talk of OEA signalling with metabolic and mitotic signal transduction of insulin receptor. OEA dose-dependently activates JNK and p38 MAPK, and inhibits insulin receptor phosphorylation. OEA inhibits insulin receptor activation, blunting insulin signalling in the downstream PI3K pathway, decreasing phosphorylation of PKB and its target GSK-3. OEA also inhibits insulin-dependent MAPK pathway, as assessed by immunoblot of phosphorylated MEK and MAPK. These effects were reversed by blocking JNK or p38 MAPK using pharmacological inhibitors (SP 600125, and SB 203580). Since OEA is an endogenous PPAR-alpha agonist, we investigated whether a pharmacologic agonist (WY 14643) may mimic the OEA effect on insulin receptor signalling. Activation of PPAR-alpha by the pharmacological agonist WY14643 in HTC hepatoma cells is sufficient to inhibit insulin signalling and this effect is also dependent on p38 MAPK but not JNK kinase. In summary, OEA inhibits insulin metabolic and mitogenic signalling by activation of JNK and p38 MAPK via PPAR-alpha.     

Involvement of receptor tyrosine phosphatase DEP‐1 mediated PI3K‐cofilin signaling pathway in Sorafenib‐induced cytoskeletal rearrangement in hepatoma cells

Sorafenib is a multikinase inhibitor that has been reported to induce cell growth inhibition through the Raf‐MAPK signaling pathway. We now report that Sorafenib treatment of Hep3B and PLC/PRF/5 human hepatoma cells also results in morphological changes and cell detachment in culture. Actin cytoskeletal analysis of Sorafenib‐exposed Hep3B cells showed a loss of polymerized F‐actin and a concomitant increase in unpolymerized G‐actin, implying that Sorafenib‐induced cell shape changes may be related to actin cytoskeletal rearrangement by inhibiting actin polymerization. Cofilin, an actin depolymerization factor, was found to be dephosphorylated and thus activated by Sorafenib, consistent with the observed increase in unpolymerized G‐actin. In examining likely mechanisms, we found that Sorafenib induced activation of the cofilin phosphatase Slingshot 1 (SSH‐1), since endogenous SSH‐1 from Sorafenib‐treated Hep3B cells was able to dephosphorylate cofilin in a concentration dependent manner. The activation of SSH‐1 by Sorafenib is probably regulated by the PI3K pathway, since Sorafenib can induce PI3K and its substrate Akt phosphorylation, and both PI3K inhibitors Ly294002 and wortmannin antagonized Sorafenib‐mediated cofilin dephosphorylation. Furthermore, we found that Sorafenib induced c‐Met phosphorylation at Tyr‐1349 but not Tyr‐1234, which is probably mediated by inhibition of receptor tyrosine phosphatase density enhanced phosphatase‐1 (DEP‐1). Our data provide evidence that besides inhibition of the Raf‐MAPK pathway, Sorafenib might also regulate hepatoma cell growth via alteration of receptor‐mediated cytoskeletal rearrangement. J. Cell. Physiol. 224: 559–565, 2010. © 2010 Wiley‐Liss, Inc.